Devices for preparing a beverage by injecting pressurized fluid into a capsule are well-known, especially in the field of producing coffee or coffee type beverages. In addition, other comestible ingredients such as chocolate or milk products can be contained within the capsule. By means of an interaction of these ingredients with a liquid, a beverage or other comestibles, such as for example soup, can be produced. The interaction can be for example an extraction, brewing, dissolution, etc. process. Such a capsule is particularly adapted to contain ground coffee in order to produce a coffee beverage by having hot water under pressure enter the capsule and draining a coffee beverage from the capsule.
The advantages of such a system are in particular the conservation and freshness of the ingredients, as well as the possibility of facilitating the operations of preparing the beverage.
Systems and methods for obtaining fluid comestibles from substances containing capsules are for example known from EP-A-512470 (counterpart of U.S. Pat. No. 5,402,707).
The capsule 101 as shown in FIG. 1 has a frustoconically-shaped cup 102 which may be filled e.g. with roasted and ground coffee 103 and which is closed by a foil-like tear face cover 104 welded and/or crimped to a flange-like rim which extends laterally from the side-wall of cup 102. A capsule holder 111 comprises a flow grill 112 with relief surface element members 113.
The capsule holder 111 is accommodated in its support 115 which has a lateral wall 124 and a bore 127 for the passage of extracted coffee beverage.
As can be seen from FIG. 1, the extraction system further comprises a water injector 107 having a water inlet channel 120 and an annular element 108 with an internal recess of which the shape substantially corresponds to the outer shape of the capsule. On its outer part, the annular member 108 comprises a spring 122 holding a ring 123 for releasing the capsule on completion of extraction.
In operation, a capsule 101 is placed in the capsule holder 111. The water injector 107 perforates the upper face of the cup 102. The lower tear face 104 of the capsule rests on the radially arranged members 113 of the capsule holder 111.
The water is injected through the channel 120 of the water injector 107 and impinges on the bed 103 of coffee. The pressure in the capsule 101 increases and the tear face 104 increasingly follows the shape of the radial opening relief members 113. Such radial opening relief members could be replaced by pyramid-shaped relief members or other shapes of relief. When the constituent material of the tear face reaches its breaking stress, the tear face tears along the relief members. The extracted coffee flows through the orifices of the flow grill 112 and is recovered in a container (not shown) beneath the bore 127.
The principles of this extraction process as far as it can be maintained in connection with the present invention can be summarized as follows:                An initially sealed capsule is inserted in capsule holder means;        The capsule holder means is then introduced associated to the water injection means of the machine such that an annular element (108 in FIG. 1) surrounds the sealed capsule.        In a first wall of the capsule at least one opening is generated.        Water entering the capsule through the opening in the first wall is interacting with the ingredients contained in the capsule while traversing the interior of the capsule and is then made to leave the capsule through at least one opening/perforation created in the second wall.        
Thereby, the ingredients in the capsule constitute the ‘bottleneck’ of the flow path of the water and will therefore cause a pressure drop between the upstream and the downstream side of the liquid flow through the capsule, which pressure drop will even increase during the interaction between the liquid and the ingredients for example due to a swelling of the ingredients. Correspondingly it has to be assured that the only water flow is actually taking place through the interior of the capsule (arrow A1) and that no water can flow from the water injector into the interstice between the annular enclosing member 108 and the exterior of the capsule 101 and then to the draining bore 127 of the device.
The arrow A2 illustrates this undesired water flow path. In other words, any water flow exterior to the capsule 101 has to be stopped by a sealing engagement being positioned in the interstice between the annular member 108 and the capsule 101 (or the annular member and the capsule holder) and in the flow path between the water injector and the beverage-draining bore. In the embodiment as shown in FIG. 1 such sealing engagement can be achieved at least to a certain degree by the pinching engagement between the annular member 108, the flange-like rim of the side wall of the capsule 101 and the capsule holder.
In case the sealing engagement is not working properly and water is flowing outside the capsule, no pressure sufficient to cause the tearing of the tear face will be built up inside the capsule or, alternatively, the pressure will be causing no complete tearing of the tear face and therefore a poor extraction of the substance. In such a scenario water will be drained from the beverage production device without having interacted or fully interacted under sufficient pressure conditions, with the ingredients contained in the capsule.
An improvement could be thought of according to which this sealing engagement is further improved by lining the inner wall of the annular member with a rubber-elastic material. With other words, according to said approach the sealing engagement is assured by structures fixed to or attached with the beverage-producing device. This has disadvantages in that after the use of a substantial number of capsules a wearing off of the fixed sealing means can take place such that the quality of the produced beverage is increasingly deteriorated by water passing the no longer properly efficient sealing.
Any ‘leak’ at the exterior of the capsule reduces the pressure build-up inside the capsule. If the pressure is insufficient, the tear membrane may not open or may open only partly. On the other hand, it is well known that a sufficient extraction pressure is a key factor for the quality of espresso-style coffee.
The present invention correspondingly aims at an improvement of the sealing engagement positioned between the liquid inlet and the beverage draining side of such a beverage production system.
It is thereby the central idea of the present invention to transfer a resilient part of the sealing engagement from the beverage production device to the capsule. The advantage is that any resilient sealing member is only used once (i.e. only with the associated capsule) such that a proper functioning of the sealing can be assured and less hygienic, cleaning and/or scale-deposition problems can occur at the sealing member.
The present invention thus especially aims at an improvement of the capsules, such that state-of-the-art beverage production devices with built-in sealing means as for example shown in EP-A-512470 can also be used in connection with a capsule according to the present invention.
EP 1 654 966 B1 relates to a capsule being configured for insertion in a beverage production device in order to make a liquid under pressure enter the capsule and to interact with the ingredients in the capsule. Thereby, the capsule comprises a resilient sealing member in the form of an O-ring or a ring having an L-shaped cross-section which is attached to the body of the capsule by means of an adhesive or by welding for example.
One possible mode to apply such a sealing means to the capsule would be by injection moulding, but this process suffers the disadvantage that it requires moulds for each body of the capsule and very high precision in the injection and tooling. Therefore, a cheaper, more convenient way is to apply the sealing means by deposition of liquid rubber on the capsule and curing the rubber on the body of the capsule.
It should be noted that the position of the sealing means as well as its distribution on the capsule is of importance to obtain efficient sealing of the capsule. It is therefore an object of the present invention to further enhance the efficiency of the sealing means provided to the capsule and in particular, to improve the positioning process of the sealing means at the capsule.
Thereby, the seal has to be accurately placed at the intersection of the rim and the side wall of the body of the capsule in order to form an L-shaped sealing portion having a concave outer surface.
Moreover, a process is sought-after which only requires a small amount of liquid rubber while maintaining an efficient sealing of the capsule. A small, discrete amount of liquid rubber enables to reduce the closing force of the beverage producing device about the capsule and it also saves important manufacturing costs.
The object is achieved by means of the features of the independent claims. The depending claims develop further the central idea of the present invention.